IBM wrote that all flash is not created equal, and that technology decisions and goals vary between manufacturers while operational challenges vary wildly between customers. EMC XtremIO, IBM wrote, is based on SSD technology, which places flash memory on a small circuit board and then into a physical disk drive enclosure that fits in a drive array chassis that is then connected to an SAS backplane via an SAS interface. "SAS adds latency, slowing data access," IBM wrote.